The Citizens suffered another loss on the road, losing 1-0 to Southampton despite having a majority of possession and shots.
"I don't know. I don't have the answer to that," the Portugal international said to reporter when asked about away form.
"Of course, it's always better to play at home, a place where we're used to being.
"But there's no excuse for that.
"We need to improve next season if we want to win again the Premier League."